1. Developing NPP algorithms for the Arctic

2. 1. Empirical chlorophyll based algorithm
Chukchi Sea

3. ANCOVA H0 – means between light levels are equal
Source
Sum-of-Squares df
Mean-Square
F-ratio P
LIGHT_CH
170.6 5
34.1
15.1
0.000
DAILY_PP_CH
3052.7 1
1354.8
Error
1428.6
634
2.3
P < 0.00 , H0 is rejected 1% 5%
15%
30%
50%
100%
1.000
0.000
0.912
0.921
0.780
0.999
0.931
1.0000
0.99 1% 5%
15%
30%
50%
100%
1.000
0.000
0.912
0.921
0.780
0.999
0.931
1.0000
0.99

4. 1. Empirical chlorophyll based algorithm
Chukchi Sea

5. 1. Empirical chlorophyll based algorithm
Resolute Bay

6. ANCOVA H0 – means between light levels are equal
Source
Sum-of-Squares df
Mean-Square
F-ratio P
LIGHT_CH
1027.1 5
205.4
11.7
0.000
DAILY_PP_CH
8696.4 1
495.6
Error
2913.1
166
17.5
P < 0.00 , H0 is rejected 1% 5%
15%
30%
50%
100%
1.000
0.000
0.581
0.322
0.998
0.205
0.988
0.999
0.502
1.0000
0.995

7. 1. Empirical chlorophyll based algorithm
Resolute Bay

8. 1. Empirical chlorophyll based algorithm
Barents Sea

9. 1. Empirical chlorophyll based algorithm
Combined dataset

10. ANCOVA H0 – means between regions are equal
Source
Sum-of-Squares df
Mean-Square
F-ratio P
LIGHT_CH
2.28 2
1.14
18.55
0.000
DAILY_PP_CH
136.48 1
Error
33.93
552
0.061
P < 0.00 , H0 is rejected
Resolute Bay
Chukchi Sea
Barents Sea
1.000
0.000
0.361

11. 1. Empirical chlorophyll based algorithm
Combined dataset
Average Chlorophyll
Resolute Bay 8.1 mg m-3
Barents Sea 4.2 mg m-3
Chukchi Sea 1.2 mg m-3
Log PP = Log Chl
ANCOVA
Chl 0.8 – 32 mg m-3
P < 0.01

12. 1.1 Surface chlorophyll vs. Euphotic zone chlorophyll

13. 1.1 Surface chlorophyll vs. Euphotic zone PP

14. 1.1 Rrs vs. Euphotic zone PP

15. 2. Model based on C:Chl ratios
Behrenfeld et al. (2005) developed a productivity model based on Chl:C ratios
and chlorophyll concentrations derived from ocean color satellite observations.
Carbon (POC) is retrieved from backscatter
Chlorophyll is retrieved from Rrs ratios (i.e OC4V4, OC3M or OC3Arc)
These are coupled with mixed layer light levels from surface PAR and K490
observations and growth rates estimated from the literature. The final equation is:
NPP = C . µ . Zeu . h(Io)
Where C is carbon, µ is growth rate, Zeu is the euphotic depth and h(Io) describes how
changes in surface light influence the depth dependent profile
of carbon fixation

16. 2. Model based on C:Chl ratios

17. 2. Model based on C:Chl ratios
Model Input
Carbon (POC) is retrieved from backscatter – Behrenfeld global relationship
Chlorophyll is retrieved from Rrs ratios - OC3Arc
Surface PAR – estimated from observations
Mixed layer light levels – estimated from observations
Growth rate – literature global, 0.5 – 2 divisions d-1
h(Io) taken from Behrenfeld and Falkowski (1997)
NPP = C . µ . Zeu . h(Io)
Model output
1. NPP euphotic zone integrated - g C m-2 day-1

18. 2.1 Results

19. 2.1 Results – adjusted model

20. Euphotic zone integrated
1st optical depth
Data
Slope r2 P
Chukchi Spring
0.36
0.61
< 0.01
0.82
0.81
Chukchi Summer
0.18
0.00
> 0.10
1.28
0.60

21. 2.2 Sensitivity to model input

22. 2.2 Sensitivity to model input
Mixed layer light levels
Surface PAR
Growth rates r2
Slope
RMS
slope
Mean
0.75
0.36
0.76
0.49
- 1 stdev
0.22
0.69
0.29
0.33
+ 1 stdev
0.57
0.88
0.64
0.65

23. 3.0 Comparison of both methods

24. Surface Chlorophyll - Spring

25. Surface Chlorophyll - Summer

26. Surface chlorophyll - Fall

27. Surface chlorophyll – Winter

28. Surface PP - Spring

29. Surface PP - Summer

30. Surface PP - Fall

31. Surface PP - Winter

32. Kd PAR – Spring + Summer